Solenoid control valves for hydraulic control systems are used to control oil under pressure that may be used to switch latch pins in switching lifters and lash adjusters in engine valve systems. Valve lifters are engine components that control the opening and closing of exhaust and intake valves in an engine. Lash adjusters may also be used to deactivate exhaust and intake valves in an engine. Engine valves may be selectively deactivated or locked out to disable operation of some cylinders in an engine when power demands on an engine are reduced. By deactivating cylinders, fuel efficiency of an engine may be improved.
Engine deactivating solenoid control valves must operate with minimum response times to maximize engine efficiency. Valve response times include valve activation response times and deactivation response times. Solenoid control valves apply a magnetic force to an armature that moves a control valve stem by activating a coil to move the armature against a biasing force that is typically provided by a spring. The magnetic force applied by the solenoid to the armature and in turn to the control valve stem should be maximized to reduce response time. The magnetic force applied by the coil can be increased by increasing the size of the coil. However, cost and weight reduction considerations tend to limit the size of the coil. Deactivation response times are adversely impacted by valve closure biasing springs, the force of which must be overcome before the valve is opened. While this delay in response times in most applications is minimal, in variable valve actuation systems, the limited time window for valve activation and deactivation is critical and must be minimized.